John Calvin Commentary Lamentations 3:13

"He hath caused the shafts of his quiver to enter into my reins." — Lamentations 3:13 (ASV)

He goes on with the same metaphor; he said in the last verse that God had leveled his bow; he now adds that his arrows had penetrated into his reins, that is, into his inward parts. But we must bear in mind what the Prophet meant: that God had dealt so severely with the people that no part, even the innermost, was sound or untouched, for his arrows had perforated their very reins. He afterwards adds: